EP0007008A1 - Process for the preparation of halogenobutenyl acrylates - Google Patents

Abstract

Halogenbutenyl acrylates of the formula H2C =? - COOCH2 - CH = CH - CH2-X (I) in which R represents a hydrogen atom or a C1 - C4 alkyl group and X represents a halogen atom can be prepared by reacting an acrylic acid salt of the formula H2C =? - COOMe (II) with 1,4-dihalobutene- (2) in a two-phase system.

Description

The invention relates to a one-step process for the preparation of halobutenyl acrylates by reacting optionally substituted acrylic acid salts with 1,4-dihalobutene- (2) in a two-phase system.

A process for the preparation of halobutenyl acrylates is already known from US Pat. No. 3,255,163. The compounds are obtained by subjecting acrylic esters to a transesterification reaction in the presence of 4-halo-2-butenols. However, this process works with a large excess of acrylic acid ester, the work-up of which is difficult and lossy. Furthermore, the starting product 4-halogen-2-bntenol- (1) can only be produced in a lossy synthesis stage. The method described is therefore technically disadvantageous.

From Synthesis 1974, page 867, it is also known to convert dibromoalkenyls with potassium acetate to corresponding bisacetates. However, the production of corresponding mono compounds is not described. Nor is there any evidence of the reaction of unsaturated carboxylic acids with dihaloalkenyls to form monosubstitution products. In order to carry out the process described, large amounts of a phase transfer catalyst, namely 22 mol%, based on the haloalkyl, are required, so that it is hardly possible to speak of catalysis here.

Both halogen atoms of 1,4-dihalobutene-2 have a high reactivity. Rapid saponifiability is an example. Substituting 1,4-dichloro-2 with sodium carbonate at 100 ⁰ C in order to be isolated only a mixture of two isomeric butenediols (Pudovi k, Z. Obsc. Chim. 19 (1949) 1185, 1950, 1005).

Due to the fact that both halogen atoms in 1,4-dichlorobutene-2 have been proven to be easy to saponify, hydrolysis to the 4-hydroxybutenyl ester had to be expected when producing corresponding chlorobutenyl esters in an alkaline-neutral aqueous medium. Surprisingly, this reaction does not occur.

• R = H, C₁ - C4- Alkyl
• X = Halogen wie z.B. Cl, Br, I
• Me= Ammonium, Alkali, Erdalkali (unter Berücksichtigung der Wertigkeit des Metall-Ions)

It has now been found that acrylic acid esters of 4-halo-2-butenols (2) can be obtained in a one-step process by reaction of optionally substituted acrylic acids with 1,4-dihalobutene- (2). This method works in a two-phase system. The alkali or alkaline earth metal salt of acrylic acid is in the aqueous phase, the organic phase consists of the excess dihalobutene, optionally diluted with a solvent. The reaction can be accelerated by using a phase transfer catalyst from the group of the quaternary ammonium phosphonium or sulfonium salts. It runs according to the following scheme:

• R = H, C ₁ -C 4 alkyl
• X = halogen such as Cl, Br, I
• Me = ammonium, alkali, alkaline earth (taking into account the valence of the metal ion)

in der

• R Wasserstoff oder einen Alkylrest mit 1 bis 4 Kohlenstoffatomen und
• X ein Halogenatom darstellt, das dadurch gekennzeichnet ist, daß man pro Mol eines Salzes der Acrylsäure der Formel (II)
  
  in der
• R Wasserstoff oder einen Alkylrest mit 1 bis 4 Kohlenatoffatomen und
• Me ein Ammonium , ein Alkali- oder Erdalkalimetallion darstellt, 1 bis 7 Mole an 1,4-Dihalogenbuten-(2) in einem Zweiphasensystem bei Temperaturen von 10 bis 140°C miteinander umsetzt.

The invention thus relates to a process for the preparation of halobutyl acrylates of the formula (I)

in the

• R is hydrogen or an alkyl radical having 1 to 4 carbon atoms and
• X represents a halogen atom, which is characterized in that, per mole of a salt of acrylic acid of the formula (II)
  
  in the
• R is hydrogen or an alkyl radical having 1 to 4 carbon atoms and
• Me represents an ammonium, an alkali or alkaline earth metal ion, 1 to 7 moles of 1,4-dihalobutene (2) are reacted with one another in a two-phase system at temperatures from 10 to 140 ° C.

Examples of alkyl substituents R which may be mentioned are methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tert-butyl, preferably methyl.

Halogen substituents X are chlorine, bromine, iodine, preferably chlorine.

Solvents which are immiscible with water, preferably aliphatic or aromatic hydrocarbons such as hexane, cyclohexane, toluene or xylene, can be used as the solvent for dihalobutene which may be used.

As alkali and / or alkaline earth metal, sodium, potassium, magnesium, calcium, strontium, barium, particularly preferably sodium or potassium, may be mentioned.

The acrylic acids are preferably reacted with dihalobutene by working with an excess of 2 to 5 moles of 1,4-dihalobutene per mole of acrylic acid. This procedure has the advantage that one can optionally work without a solvent. With this preferred procedure, working up is made easier. The two phases are separated from one another after the reaction and the organic phase is subjected to fractionation. It is particularly simple since the excess dichlorobutene can easily be separated off in a first column because of its relatively low boiling point. In a second column, the ester is obtained in high purity as a side stream. The esters are obtained in yields of 60-78% based on the acid used and 70-80% based on dichlorobutene. The excess dichlorobutene is completely recovered.

The new process also has the advantage over the known process that cheap, dilute acrylic acid can be used, as is the case in industrial processes. In addition, no excess of this compound is required. The unreacted acrylic acid can be reused in the aqueous phase.

The reaction is carried out by heating a stirred two-phase mixture of the salt of acrylic acid dissolved in water and the halogen compound. In addition to the phase transfer catalyst, various known polymerization inhibitors may be added to the mixture, for example hydroquinone N-nitrosodiphenylamine, p-tert-butyl catechol, 4-methoxyphenol, phenothiazine or mixtures of two or more stabilizers. The reaction is preferably carried out at temperatures in the range from 60 to 100 ° C., particularly preferably in the range from 80 to 95 ° C.

Quaternary ammonium, phosphonium and sulfonium compounds are suitable as any phase transfer catalysts present. Their general formula is RR'R "R '" E ⁺ X ^- , in which the radicals R, R', R ", R"'are aliphatic or aromatic radicals, which may optionally be hydroxyl-substituted, and E is a nitrogen or phosphorus atom mean. X is an anion. The general formula of the sulfonium compounds is RR 'R "S ⁺ X ^- with the same meaning of the residues.

• Tetrabutylammoniumhalogenid Tetraoctylammoniumhalogenid Octyl-tributylammoniumhalogenid Octadecyltributylammoniumhalogenid Octyl-bis-(hydroxyäthyl)-benzylammoniumhalogenid Dodecyl-bis-(hydrozypropyl)-benzylammoniumhalogenid Octadecyl-dimethyl-benzylammoniumhalogenid

Ammonium compounds are preferably used. Examples of the latter are:

• Tetrabutylammonium halide, tetraoctylammonium halide, octyl tributylammonium halide, octadecyltributylammonium halide Octyl-bis (hydroxyethyl) benzylammonium halide dodecyl-bis (hydrozypropyl) benzylammonium halide octadecyl-dimethyl-benzylammonium halide

The catalyst is used in an amount of 0.01 to 10 mol%. Amounts of 0.1 to 5.0, particularly preferably 0.2 to 1.0 mol% are preferred.

The unsaturated esters that can be prepared by the process are valuable comonomers for radical-initiated polymerizations. Because of the simplicity of the process, they are also available on an industrial scale for the first time. Due to the lability of the γ-chlorine atom, they are suitable for the production of γ-amino or γ-acyloxy-substituted acrylic acid esters.

example 1

= 1.4808.

It is made from 191.3 g of methacrylic acid (90%, 2 mol) 331.5 g of water and 175.2 g of 50% sodium hydroxide solution (2.2 mol) with the addition of 2.5 g of N-nitrosodiphenylamine, 2.5 g 4-methoxyphenol and ^{8 g} (C _12-18 H _29-37 ) N⊕ (CH ₂ CHOHCH ₃ ) ₂ -CH ₂ C ₆ H ₅ ) Cl⊖ (70%) a solution of the sodium salt of methacrylic acid and heated this to 90 ° C. Then 750 g (6 mol) of 1,4-dichlorobutene-2 are added with stirring within 10 minutes. After heating for 1 hour at the same temperature, 8 g of NaOH (50%) are added and the mixture is left to react for a further 2 hours. The mixture is cooled and stirring is stopped. After separation of the phases, the lower aqueous phase is removed and the organic phase is distilled in vacuo using a packed column (height 30 cm). As the first fraction, 530 g of dichlorobutene are separated off (4.24 mol) at 25 to 58 ° C. (2.3 mb). The second fraction (bp 72 to 80 ° C / 2 mb) contains the pure 4-chloro-2-butenyl methacrylate. 242.2 g (= 69.4% of theory Δ 1.39 mol) are isolated. 44.9 g of a low-viscosity substance remain as residue, which due to the thin-layer chromatogram still contains about 20 to 30% of the ester. The distilled chlorobutenyl ester is stabilized with 50 ppm 4-methoxyphenol.

= 1.4808.

Example 2

Analogously to Example 1, the chlorobutenyl methacrylic acid ester is prepared using only 4 mol (500 g) 1,4-dichlorobutene-2. After working up according to Example 1, 208.5 g of ester (59.6% of theory) are obtained, and 275 g of dichlorobutene (2.2 mol) are recovered.

Example 3

Analogously to Example 1, the reaction is carried out using 8 mol of 1,4-dichlorobutene-2 (1000 g). After working up, 271.4 g (77.7% of theory) of ester are isolated.

Example 4

A solution of the Na salt of methacrylic acid is prepared from 95.65 g (1 mol) of methacrylic acid (90%), 87.6 g (50%) of NaOH and 165.8 g of water. 1.2 g of N-nitrosodiphenylamine and 1.2 g of 4-methoxyphenol are added and 250 g (2 mol) of 1,4-dichlorobutene-2 are run in rapidly at 90 ° C. with stirring. After 1 hour, 4 g of 50% sodium hydroxide solution are added and the mixture is then heated with stirring for a further 2 hours. The phases are then separated. 0.78 mol of NaCl can be detected by argentometry in the aqueous phase. The organic phase is distilled as described. In addition to 169.0 g (135 mol) of dichlorobutene, 67.5 g of 4-chlorobutenyl methacrylate are obtained, which is 38.5% of theory.

Clearly poorer yields are obtained without a catalyst.

Example 5

An aqueous solution of sodium acrylate is prepared from 216.2 g of acrylic acid (100% = 3 mol), 262.8 g of NaOH (50%) and 497 g of water, and 3.7 g of N-nitrosodiphenylamine and 3.7 g 4-methoxyphenol is added for stabilization. Furthermore, 12 g of the quaternary ammonium salt used in Example 1 are added. At 90 ° C., 1125 g (9 mol) of 1,4-dichlorobutene are run in, 15.9 g of Na ₂ CO ₃ are added after 1 hour and the mixture is left to react at 90 ° C. for a further 2 hours. After phase separation the organic layer distilled in vacuo. 286.0 g (1.78 mol) of 4-chloro-2-butenyl acrylate (59.4% of theory) are obtained. 641 g (5.13 mol) of dichlorobutene are recovered.

Claims (9)

1. Process for the preparation of halobutyl acrylates of the formula (I)

in the R is hydrogen or an alkyl radical having 1 to 4 carbon atoms and X represents a halogen atom,
characterized in that per mole of a salt of acrylic acid according to formula (II)

in the R is hydrogen or an alkyl radical having 1 to 4 carbon atoms and Me represents an ammonium, an alkali or alkaline earth metal atom equivalent: 1 to 7 mol of 1,4-dihalobutene- (2) in a two-phase system at temperatures of 10 to 140 ° C. 2. The method according to claim 1, characterized in that the reaction temperature is 60 to 100 ° c. 3. Process according to claims 1 and 2, characterized in that the reaction temperature is 80 to 95 ° C. 4. Process according to Claims 1 to 3, characterized in that 2 to 5 moles of 1,4-dihalobutene (2) are used per mole of a salt of acrylic acid according to formula (II). 5. The method according to claims 1 to 4, characterized in that the reaction is carried out in the presence of a phase transfer catalyst from the group of quaternary ammonium, phosphonium or sulfonium salts. 6. The method according to claim 5, characterized in that the phase transfer catalyst is used in amounts of 0.01 to 10 mol%. 7. The method according to claims 5 and 6, characterized in that the phase transfer catalyst is present in amounts of o, 1 to 5 mol%. 8. The method according to claim 5, characterized in that the phase transfer catalyst is present in amounts of 0.2 to 1 mol%. 9. halobutenyl acrylates, prepared by a process of claims 1 to 8.